- 03 February 2021
- Journal article
The importance of supplementary immunisation activities to prevent measles outbreaks during the COVID-19 pandemic in Kenya
- BMC Medicine
Background: The COVID-19 pandemic has disrupted routine measles immunisation and supplementary immunisation activities (SIAs) in most countries including Kenya. We assessed the risk of measles outbreaks during the pandemic in Kenya as a case study for the African Region.
Methods: Combining measles serological data, local contact patterns, and vaccination coverage into a cohort model, we predicted the age-adjusted population immunity in Kenya and estimated the probability of outbreaks when contact-reducing COVID-19 interventions are lifted. We considered various scenarios for reduced measles vaccination coverage from April 2020.
Results: In February 2020, when a scheduled SIA was postponed, population immunity was close to the herd immunity threshold and the probability of a large outbreak was 34% (8–54). As the COVID-19 contact restrictions are nearly fully eased, from December 2020, the probability of a large measles outbreak will increase to 38% (19–54), 46% (30–59), and 54% (43–64) assuming a 15%, 50%, and 100% reduction in measles vaccination coverage. By December 2021, this risk increases further to 43% (25–56), 54% (43–63), and 67% (59–72) for the same coverage scenarios respectively. However, the increased risk of a measles outbreak following the lifting of all restrictions can be overcome by conducting a SIA with ≥ 95% coverage in under-fives.
Conclusion: While contact restrictions sufficient for SAR-CoV-2 control temporarily reduce measles transmissibility and the risk of an outbreak from a measles immunity gap, this risk rises rapidly once these restrictions are lifted. Implementing delayed SIAs will be critical for prevention of measles outbreaks given the roll-back of contact restrictions in Kenya.
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Mburu, C., Ojal, J., Chebet, R., Akech, D., Karia, B., Tuju, J., Sigilai, A., Abbas, K., Jit, M., Funk, S., Smits, G., van Gageldonk, P., van der Klis, F., Tabu, C., Scott, J., CMMID COVID-19 Working Group, Nokes, D., Flasche, S. & Adetifa, I. 2021, 'The importance of supplementary immunisation activities to prevent measles outbreaks during the COVID-19 pandemic in Kenya', BMC Medicine, 19(1), article no: 35. https://doi.org/10.1186/s12916-021-01906-9